Warmup 10/19/15 Imagine you had a huge pile of pennies. Is there a way you could figure out how many you have without having to count every single one? Objective Tonight’s Homework To become familiar with how chemists count large numbers of atoms pp 203: 34, 35, 40

Notes on Avogadro’s Number What does the word “dozen” mean?

Notes on Avogadro’s Number What does the word “dozen” mean? It means that you have 12 of something. Anything. A “dozen” eggsA “dozen” pencils

Notes on Avogadro’s Number Scientists have a special number for measuring atoms. It’s called Avogadro’s Number. When using this term to measure, we call the quantity a “mole” (write it as “mol” after a number)

Notes on Avogadro’s Number Scientists have a special number for measuring atoms. It’s called Avogadro’s Number. When using this term to measure, we call the quantity a “mole” (write it as “mol” after a number) If I have 1 mole of some element, it will have a weight in grams equal to its atomic number. Examples: 1 mole of H weighs g 1 mole of Au weighs 197 g

Notes on Avogadro’s Number So how many molecules or atoms or things does it take to get 1 mole of them? A lot x10 23 things = 1 mole Box this and memorize!

Notes on Avogadro’s Number Don’t let this freak you out. A “mole” is just like a “dozen” but way bigger x10 23 instead of mole of 1 mole of 1 mole of sulfur copperaluminum

Notes on Avogadro’s Number A “dozen” eggsA “dozen” pencils 1 “mole” of aluminum 1 “mole” of copper 1 “mole” of sulfur

Notes on Avogadro’s Number Ok, everyone have the concept down? Let’s do a practice problem. Example: Find the mass of.25 moles of SO 2

Notes on Avogadro’s Number Ok, everyone have the concept down? Let’s do a practice problem. Example: Find the mass of.25 moles of SO 2 Remember, we defined moles so that the amu ends up being the same as grams. So if we can find the molar weight (AMUs) of SO 2, we can get what we need. S = 32O = 16so SO 2 = 64 amu

Notes on Avogadro’s Number Ok, everyone have the concept down? Let’s do a practice problem. Example: Find the mass of.25 moles of SO 2 Remember, we defined moles so that the amu ends up being the same as grams. So if we can find the molar weight (AMUs) of SO 2, we can get what we need. S = 32O = 16so SO 2 = 64 amu Last, we do dimensional analysis. =.25 mol SO 2 64 grams 1 1 mol SO 2

Notes on Avogadro’s Number Ok, everyone have the concept down? Let’s do a practice problem. Example: Find the mass of.25 moles of SO 2 Remember, we defined moles so that the amu ends up being the same as grams. So if we can find the molar weight (AMUs) of SO 2, we can get what we need. S = 32O = 16so SO 2 = 64 amu Last, we do dimensional analysis. = 16 grams.25 mol SO 2 64 grams 1 1 mol SO 2

Practicing with Moles Practice the following problems below to make sure you get the idea. (Note: These could be on our HW quiz!) Convert 1.26 moles of NbI 5 to grams Convert 86.2 grams of C 2 H 4 to moles Convert 4.2 grams of H 2 O to moles Convert moles H 2 SO 4 to molecules

Practicing with Moles Practice the following problems below to make sure you get the idea. (Note: These could be on our HW quiz!) Convert 1.26 moles of NbI 5 to grams g/mol * 1.26 mol = g Convert 86.2 grams of C 2 H 4 to moles 1 mol / g * 86.2 g = 3.08 mol Convert 4.2 grams of H 2 O to moles 1 mol / g * 4.2 g = mol Convert moles H 2 SO 4 to molecules 6.022x10 23 molecules / mol *0.943 mol = 5.68x10 23 molecules

Exit Question Which weighs more: 200 moles of H 2 or 30 moles of C? a) The H 2 b) The C c) They weigh the same d) Not enough info